It sounds like a shady pop-up ad, but the penis enlarger is legit. Dr. James Elist's Penuma, which comes in sizes L, XL and XXL, is a silicone sleeve that's inserted under the skin of a man's penis to make it longer and thicker.

Men have desired larger penises probably since Adam compared his to the evil serpent who convinced Eve to take a bite of forbidden fruit (a metaphor you've never thought of until now, right?).

And now they can have it, as long as they're willing to shell out $13,000 and forgo sex for six weeks.

As GQ reports in a lengthy investigation of the surgery and its inventor, Elist is the only doctor permitted by the FDA to perform the Penuma procedure. The doctor has inserted approximately 1,300 penile implants, the magazine reports, and a clinical study commissioned by Elist demonstrates a success rate of over 95 percent among men who agreed to participate in the study.

Previous penis enlargement options have included injecting collagen or cadaver cells, while some practitioners cut a ligament in the groin so the penis hangs lower, making it seem longer. Both of these practices have caused problems such as a lumpy appearance or complications with erections, GQ reports.

WARNING: Graphic image below.

Here's a visual that shows how the surgery works:

While having a monopoly on his silicone penis enlargement sounds pretty darn lucrative on its own, Elist is currently pushing for the FDA to approve his product for sale so that other professionals can perform the procedure.

CORRECTION: A previous version of this article stated that the Penuma was the only FDA-approved penile implant. The device is not approved by the FDA, but has been cleared by the organization to be used commercially. Other devices have been approved to treat erectile dysfunction.